MALE (Reuters) - The Maldives Supreme Court on Friday ordered security forces to take action against anyone who violates the constitution, after the archipelago's election chief said it will hold a presidential run-off on September 28 as scheduled despite a court ruling to postpone it.

In a special court session after midnight, six out of seven Supreme Court judges ruled that the court's earlier order of September 23 to postpone the run-off should be upheld.

In its order, the court told security forces to "stop any individual from disobeying" the postponement. The run-off vote is being delayed after a complaint of voting irregularities from the losing party.

"Since it is stated clearly (in the constitution), it is illegal to disobey or challenge a Supreme Court order within the jurisdiction of the Maldives," the order said.

Election Commissioner Fuwad Thowfeek, amid increasing international pressure on the government to push ahead with a run-off, had said on Thursday that the Supreme Court had no right to override the constitution, which stipulates that a run-off vote must be held within three weeks of the first round.

"We don't believe any organization or institution can overshadow the constitution. So we are working toward the constitution," he told Reuters, amid calls for his arrest by some politicians for contempt of court.

"I don't care about punishment from the Supreme Court. They should uphold the constitution," he said.

The first round of voting, on September 7, was won by ex-president Mohamed Nasheed, whose removal from power 20 months ago ignited months of unrest.

"We welcome the Elections Commission decision. I ask all parties to respect this decision," tweeted Nasheed, forced from office in February 2012 when mutinying police and soldiers armed opposition demonstrators and gave him an ultimatum to leave.

Nasheed secured 45.45 percent in the first round, short of the 50 percent needed for outright victory, and his party promptly announced mass protests against the postponement.

The run-off was expected to help end months of political turmoil in the Indian Ocean archipelago that began after Nasheed was ousted.

Soon after Thowfeek's announcement, police set up barricades near the election commission's headquarters, where the five-member Election Committee held its meeting to decide the run-off should proceed on Saturday.

A Reuters reporter saw police taking away at least three people in the crowd gathered outside the building in handcuffs.

Nasheed said there should not be any doubt over this Saturday's election, addressing thousands of supporters gathered near the country's tsunami monument in Male, the capital of the chain of islands that is home to a series of luxury hotels popular with tourists.

CONSTITUTIONAL CRISIS

Abdulla Yameen, half-brother of longtime ruler Maumoon Abdul Gayoom, placed second in the presidential poll, just ahead of Gasim Ibrahim, a tourism and media tycoon who was finance minister under Gayoom.

Gasim's Jumhoory Party (JP) had asked the Supreme Court to annul the first-round result, alleging voting irregularities, a move that Nasheed's Maldivian Democratic Party (MDP) dismissed as unconstitutional.

Yameen's vice presidential candidate Mohamed Jameel Ahmed said the Election Commission did not have the mandate to hold the election against the will of the Supreme Court.

"Our view is very clear: the election cannot go ahead. We will not allow it, no one in the country will allow it," he said.

Nasheed's successor, President Mohamed Waheed, under pressure to hold the run-off as scheduled, asked the international community to refrain from making statements on the election.

"Irresponsible statements by foreign governments and international organizations would not be helpful in consolidating democracy in the country," he said.

Acting Interior Minister Ahmed Shafeeu said in a statement that "violating the Supreme Court order or assisting such an action is a crime. The government will take necessary action against such persons."

Finance Minister Abdulla Jihad said his ministry would not provide any funds required by the Election Commission for the run-off vote due to the Supreme Court order.

The Election Commission said it had already brought down international poll monitors from the European Union and Commonwealth.

Although the MDP controls parliament, the police have already informed the election commission that they will abide by the Supreme Court ruling.

Nasheed served for three years as the Maldives' first democratically elected president. Protests by his supporters after his ouster were met with a heavy police crackdown that tarnished the Maldives' image as a tranquil holiday paradise.

Critical challenges facing the next president include a rise in Islamist ideology, human-rights abuses and a lack of investor confidence after the government canceled the Maldives' biggest foreign investment project with India's GMR Infrastructure.